This invention relates to an engine synchronization system and more particularly to an engine synchronization system for the turbo jet engines in a twin-engine aircraft.
It is well known that the synchronization of the speed between the power plants of twin-engine aircraft offer a number of advantages. For example, the synchronization of the engines reduces or eliminates crew and passenger fatigue due to the vibration caused by non-synchronized engines. It is also believe that engine synchronization may increase the economy of the aircraft and the useful life of the engines.
In the past, pilots have tried to obtain synchronization by careful engine control relying on their ears for determining when the xe2x80x9con speedxe2x80x9d conditions were reached. More recently, pilots have had the aid of automatic synchronization systems as disclosed in an article entitled xe2x80x9cFlying in Stepxe2x80x9d in the Mar. 21, 1952 issue of Flight.
In modern, twin-jet engine aircraft, a pilot may manually control the power by means of the throttle control lever or quadrant. In some aircraft, the throttle control is integrated with the flight control system and, under normal flight conditions, controlled thereby. For example, one such system is disclosed in my U.S. Pat. No. 5,613,652 entitled xe2x80x9cAircraft Auto Throttle Systemxe2x80x9d which issued on Mar. 25, 1997, and is incorporated herein in its entirely by reference.
It is now believed that there may be a significant commercial demand for an improved engine synchronization system which can be incorporated in an autothrottle system. One advantage of the system in accordance with the present invention resides in the use of a split shaft assembly and a sprag clutch. The split shaft assembly allows one portion of the shaft to rotate independently of the other portion. The sprag clutch allows the manual throttle controls to be on the same shafts and to move without rotation of the shaft. At the same time, the manual control has authority over a possible runaway or locked servo motor.
It is believed that the systems, in accordance with the present invention, will accurately synchronize the turbojet engines in a twin-jet aircraft, reduce vibration, improve crew and passenger comfort, increase engine efficiency and the useful life of the engines. In addition, such systems are relatively inexpensive to add to autothrottle controls, durable and reliable. In addition, the engine synchronization system in accordance with the present invention has essentially zero play and provides the minute adjustment that is required for turbines which rotate at about 20,000 rpm.
In essence, the present invention contemplates an engine synchronization system for twin turbojet engines. The engine synchronization system includes means for selecting a power output, means for producing a first output signal in response to the speed of a first engine and means for producing a second output signal in response to the speed of a second engine. The system also includes averaging means for averaging the speed of the engines and means for detecting any differences in the averaging speed and the speed of each engine. A servo driven throttle control is provided for advancing and retarding the speed of each engine to match the average speed to thereby synchronize the engines.
The servo driven throttle control includes a first and a second servo motor and a split shaft assembly including first and second output shafts which are disposed on a common axis. The first of the output shafts is operatively connected or locked to the first of the servo motors while the second of the output shafts is connected to or locked to the second of the servo motors. Each of the shafts are free to rotate independently of the other. The servo driven throttle control also incorporates a pair of sprag clutches with one of the clutches disposed between each of the shafts which allows a manual throttle control to rotate about the shaft without rotating the shaft and for providing authority to the manual throttle control. The shafts are then driven by the servo motors and control the engine speed through the clutches.
It should be recognized that the engine synchronization system, in accordance with the present invention, may be implemented in analogue, digital or programmed technology utilizing apparatus and techniques which are well within the skill of the art in view of the teachings which follow hereinafter. However, the present invention is described with respect to exemplary embodiments employing a suitable programmed micro computer or the like.
The invention will now be described in connection with the accompanying drawings.